Rapid communication: Period2 gene silencing increases the synthesis of α_s–casein protein in bovine mammary epithelial cells

Period2 (PER2), a core clock gene, encodes a circadian rhythm protein which has been shown to control mammary metabolism in rodents. Whether PER2 regulates milk component synthesis such as α_s–casein protein in bovine mammary cells is unknown. Thus, we used gene silencing technology to determine if PER2 silencing could affect α_s–casein synthesis and cell growth in cultured primary bovine mammary epithelial cells (BMEC). The BMEC were established by enzymatic digestion of mammary tissue from mid-lactation cows. A transient-transfection technique was used to insert a small interfering RNA (siRNA) oligonucleotide specific for PER2 to inhibit transcription. Control and siRNA-transfected cells were cultured for 48 h. qRT-PCR and ELISA analysis showed that PER2 silencing enhanced the synthesis of 2 kinds of α_s–casein (P < 0.05) through upregulating the mRNA level of CSN1S1 and CSN1S2 (P < 0.01). Furthermore, the 3-(4, 5-dimethyl-2-thiazolyl)- 2, 5-diphenyl-2-H-tetrazolium bromide (MTT) results demonstrated that cell proliferation was not affected (P > 0.05). These data led us to hypothesize that PER2 protein may potentially play an important role in the control of milk protein synthesis and, hence, represents a target that can be used to regulate protein synthesis rate during lactation.